In general, techniques are disclosed for automatic discovery and load balancing of virtual service instances of a plurality of cloud data centers within a Software Defined Networking (SDN) or a Network Functions Virtualization (NFV) environment. In one example, a global load balancing device (GLB) of a first cloud data center receives, from an SDN controller, address information for a first set of virtual service instances provided by the first cloud data center and a hostname of a domain for which to perform load balancing across the plurality of cloud data centers. The GLB device requests, from a domain name server (DNS) for the domain, address information for other sets of virtual service instances provided by other cloud data centers. Further, the GLB device applies a load balancing algorithm to direct network traffic to one or more of the virtual service instances provided by the plurality of cloud data centers.